The present invention relates to a method and apparatus for controlling the storage time of a charge storing photoelectric converter.
A charge storing photoelectric converter composed of a plurality of light-detecting elements is well known in the art. The storage time of such a converter is controlled by one of the following methods:
(1) After the elapse of a selected storage time, the stored video signal is read out. Checking is then carried out to determine whether the signal level of the read-out video signal is appropriate for handling by the processing circuit. If the signal level is not appropriate, the storage time is set to another value and the above procedure is repeated until a video signal of the proper level is obtained. (This method is disclosed in Unexamined Published Japanese Patent Application No. 110209/80.)
(2) A single monitor light-detecting element is positioned adjacent to the plurality of light-detecting elements and the storage of video signals in the latter is completed when a predetermined amount of light is received by the monitor light-detecting element (See Unexamined Published Japanese Patent Application No. 64711/82).
(3) Each of the light-detecting elements is provided with a terminal for detecting the amount of light received and the storage of video signals is completed when any one of the terminals has received a predetermined amount of light.
The first method involves several storage operations before a video signal having the desired level is obtained, so that a prolonged period of time is necessary before the subsequent step of signal processing becomes possible. In the second method, the amount of charge stored in more than one light-detecting element is determined on the basis of the amount of light received by a single monitor element, and therefore, the peak value of the output video signal has undesirably great variations. The third method which makes use of the charges stored in one of the light-detecting elements responsible for actual photoelectric conversion outputs only a low quality signal.
Therefore, the primary object of the present invention is to provide a method and apparatus capable of determining the right storage time of a charge storing photoelectric converter without experiencing the defects of the conventional techniques.